In the production of a glass plate, a conveying mechanism is necessary for glass plate formation from a molten-state glass or for annealing the glass plate formed. This conveying mechanism generally comprises conveying rolls, and disk rolls are being used as one species of such conveying rolls.
FIG. 1 is a diagrammatic view illustrating a disk roll 10 as an example. This disk roll 10 is produced in the following manner. An aqueous slurry containing inorganic fibers, a filler, a clay as a binder, and other ingredients is formed into a sheet by a papermaking method and dried to form a platy material having a thickness of about several millimeters. Ring-shaped disks are punched out of the resultant dried base material for disk rolls, and these disks 12 are fitted by insertion onto a metallic shaft 11 serving as a rotating shaft. Thus, a roll-form stack is obtained. The whole stack is compressed through flanges 13 disposed respectively on both ends, and these disks 12 in this slightly compressed state are fastened with nuts 15 or the like. In the disk roll 10 thus obtained, the peripheral surface of the disks 12 functions as a conveying surface.
Such disk rolls 10 are mounted in a glass plate production apparatus 100 as shown in FIG. 2, and used for glass plate formation and conveyance. This glass plate production apparatus 100 is an apparatus in which a molten glass 110 is continuously discharged from a melting furnace 101 through a linear slit 102 of the furnace, and this strip-form molten glass 110 discharged is caused to descend and is cooled and hardened during the descent to thereby produce a glass plate. The disk rolls 10 function as a pair of drawing rolls, which hold the strip-form molten glass 110 therebetween and forcedly send it downward. The disk rolls 10 just after the production thereof are constituted of disks 12 obtained by merely shaping the aqueous slurry. When the disk rolls 10 in this state are used for conveyance, the clay is sintered by the heat transferred upon contact with the molten glass 110. The disks 12 thus harden, and strength and wearing resistance are imparted thereto. The hardening proceeds with repetitions of contact with the molten glass 110.
Alumina fibers and aluminosilicate fibers are extensively used as the inorganic fibers from the standpoint of heat resistance. Alumina fibers and aluminosilicate fibers crystallize upon heating or the crystallization thereof proceeds with heating, whereby these fibrous materials increase in hardness. Although alumina fibers and aluminosilicate fibers can contribute to an improvement in wearing resistance through the hardening thereof, neither the alumina fibers nor the aluminosilicate fibers crystallize at the surface temperature of the molten glass 110 (about 800° C.).
A disk roll containing mica particles which are incorporated in order to impart heat resistance and wearing resistance has been proposed (see, for example, patent document 1). However, with the formulations using alumina fibers or aluminosilicate fibers, the contribution of these fibers to wearing resistance is not great as stated above.
Patent Document 1: JP-B-59-28771